[ssl] Support ssl_encapsulate on server side

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/13018)

1 files changed, 81 insertions, 25 deletions

diff --git a/ssl/statem/extensions_srvr.c b/ssl/statem/extensions_srvr.c
index 9ec48ef56a..eb24d0a19e 100644
--- a/ssl/statem/extensions_srvr.c
+++ b/ssl/statem/extensions_srvr.c
@@ -1696,6 +1696,7 @@ EXT_RETURN tls_construct_stoc_key_share(SSL *s, WPACKET *pkt,
     unsigned char *encodedPoint;
     size_t encoded_pt_len = 0;
     EVP_PKEY *ckey = s->s3.peer_tmp, *skey = NULL;
+    const TLS_GROUP_INFO *ginf = NULL;
 
     if (s->hello_retry_request == SSL_HRR_PENDING) {
         if (ckey != NULL) {
@@ -1733,37 +1734,92 @@ EXT_RETURN tls_construct_stoc_key_share(SSL *s, WPACKET *pkt,
         return EXT_RETURN_FAIL;
     }
 
-    skey = ssl_generate_pkey(s, ckey);
-    if (skey == NULL) {
-        SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_TLS_CONSTRUCT_STOC_KEY_SHARE,
-                 ERR_R_MALLOC_FAILURE);
+    if ((ginf = tls1_group_id_lookup(s->ctx, s->s3.group_id)) == NULL) {
+        SSLfatal(s, SSL_AD_INTERNAL_ERROR,
+                 SSL_F_TLS_CONSTRUCT_STOC_KEY_SHARE, ERR_R_INTERNAL_ERROR);
         return EXT_RETURN_FAIL;
     }
 
-    /* Generate encoding of server key */
-    encoded_pt_len = EVP_PKEY_get1_tls_encodedpoint(skey, &encodedPoint);
-    if (encoded_pt_len == 0) {
-        SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_TLS_CONSTRUCT_STOC_KEY_SHARE,
-                 ERR_R_EC_LIB);
-        EVP_PKEY_free(skey);
-        return EXT_RETURN_FAIL;
-    }
+    if (!ginf->is_kem) {
+        /* Regular KEX */
+        skey = ssl_generate_pkey(s, ckey);
+        if (skey == NULL) {
+            SSLfatal(s, SSL_AD_INTERNAL_ERROR,
+                     SSL_F_TLS_CONSTRUCT_STOC_KEY_SHARE,
+                     ERR_R_MALLOC_FAILURE);
+            return EXT_RETURN_FAIL;
+        }
 
-    if (!WPACKET_sub_memcpy_u16(pkt, encodedPoint, encoded_pt_len)
-            || !WPACKET_close(pkt)) {
-        SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_TLS_CONSTRUCT_STOC_KEY_SHARE,
-                 ERR_R_INTERNAL_ERROR);
-        EVP_PKEY_free(skey);
+        /* Generate encoding of server key */
+        encoded_pt_len = EVP_PKEY_get1_tls_encodedpoint(skey, &encodedPoint);
+        if (encoded_pt_len == 0) {
+            SSLfatal(s, SSL_AD_INTERNAL_ERROR,
+                     SSL_F_TLS_CONSTRUCT_STOC_KEY_SHARE,
+                     ERR_R_EC_LIB);
+            EVP_PKEY_free(skey);
+            return EXT_RETURN_FAIL;
+        }
+
+        if (!WPACKET_sub_memcpy_u16(pkt, encodedPoint, encoded_pt_len)
+                || !WPACKET_close(pkt)) {
+            SSLfatal(s, SSL_AD_INTERNAL_ERROR,
+                     SSL_F_TLS_CONSTRUCT_STOC_KEY_SHARE,
+                     ERR_R_INTERNAL_ERROR);
+            EVP_PKEY_free(skey);
+            OPENSSL_free(encodedPoint);
+            return EXT_RETURN_FAIL;
+        }
         OPENSSL_free(encodedPoint);
-        return EXT_RETURN_FAIL;
-    }
-    OPENSSL_free(encodedPoint);
 
-    /* This causes the crypto state to be updated based on the derived keys */
-    s->s3.tmp.pkey = skey;
-    if (ssl_derive(s, skey, ckey, 1) == 0) {
-        /* SSLfatal() already called */
-        return EXT_RETURN_FAIL;
+        /*
+         * This causes the crypto state to be updated based on the derived keys
+         */
+        s->s3.tmp.pkey = skey;
+        if (ssl_derive(s, skey, ckey, 1) == 0) {
+            /* SSLfatal() already called */
+            return EXT_RETURN_FAIL;
+        }
+    } else {
+        /* KEM mode */
+        unsigned char *ct = NULL;
+        size_t ctlen = 0;
+
+        /*
+         * This does not update the crypto state.
+         *
+         * The generated pms is stored in `s->s3.tmp.pms` to be later used via
+         * ssl_gensecret().
+         */
+        if (ssl_encapsulate(s, ckey, &ct, &ctlen, 0) == 0) {
+            /* SSLfatal() already called */
+            return EXT_RETURN_FAIL;
+        }
+
+        if (ctlen == 0) {
+            SSLfatal(s, SSL_AD_INTERNAL_ERROR,
+                     SSL_F_TLS_CONSTRUCT_STOC_KEY_SHARE,
+                     ERR_R_INTERNAL_ERROR);
+            OPENSSL_free(ct);
+            return EXT_RETURN_FAIL;
+        }
+
+        if (!WPACKET_sub_memcpy_u16(pkt, ct, ctlen)
+                || !WPACKET_close(pkt)) {
+            SSLfatal(s, SSL_AD_INTERNAL_ERROR,
+                     SSL_F_TLS_CONSTRUCT_STOC_KEY_SHARE,
+                     ERR_R_INTERNAL_ERROR);
+            OPENSSL_free(ct);
+            return EXT_RETURN_FAIL;
+        }
+        OPENSSL_free(ct);
+
+        /*
+         * This causes the crypto state to be updated based on the generated pms
+         */
+        if (ssl_gensecret(s, s->s3.tmp.pms, s->s3.tmp.pmslen) == 0) {
+            /* SSLfatal() already called */
+            return EXT_RETURN_FAIL;
+        }
     }
     return EXT_RETURN_SENT;
 #else